Relay-regulating circuits



INVENTOR BY I?.

AT`T0RNE'Y R. H. LINDSAY Filed Nov.

RELAY REGULATNG CIRCUITS April 14, 1931.

. systems generally,

Patented Apr. 14, 1931 UNTLD STATES PATENT OFFCE JERSEY, ASSIGNOR T0 AMERICAN TELE- A CORPORATION OF NEW YORK RELA Y-REG ULATING CIRCUITS Application led November 1, 1928. Serial No. 316,606.

This invention relates to regulating circuits for telephone systems and for signaling and particularly to regulating circuits employing trains of relays.

In this invention, there will be described regulating circuits consisting principally of trains of relays the purpose of which is to correct for variations in the magnitude of alternating current flowing in a telephone or signaling circuit. Due to the substantial variations in attenuation in the transmitting medium employed in a telephone or signaling system caused by changes in numerous conditions, as, for example, in the weather, a regulating circuit of the above-mentioned type is deemed necessary. It is the object of the regulating circuit to correct for such variations in attenuation in order to maintain the transmission equivalent of the transmitting medium highly constant. The principles of this invention may be applied to the automatic pilot channel of a carrier system to produce automatic corrections in the transmission equivalent of the circuit.

While this invention will be pointed out with p articularity in the appended claims, the invention itself, both as to its further ob'- jects and features, will be better understood when read in connection with the aecompanying drawing, in which Figure l shows a regulating circuit which includes a pair of -trains of relays for changing the total attenuation in arithmetical progression, introduced by a plurality of attenuation pads having magnitudes in geometric progression, and in which Fig. 2 shows a circuit arrangement which may be associated with the pair of trains of the same end,

Referring to Fig. 1 of the drawing, there is shown a pair of relay trains, there being two relays for each step, one in eachtrain.

relays to accomplish A transmission circuit is shown between the reference characters e and f and signaling energy flows thereover. Four attenuation pads may be associated with the transmission circuit, and these may have magnitudes corresponding to one, two, four and eight transmission units. Relays A1 and Bl of the respective trains comprise the first Istep and control the first attenuation pad of one transmission unit, relays A2 and B2, the second, and so on, the number of pairs of relays employed depending upon the number of attenuation pads there are in the system. Each of the A relays has a single winding, and, with the exception of the last A relay, four armatures, the iirst and last two of which are mechanically coupled by means of a ba-r of insulation. The last A relay has but two armatures. Each of the B relays includes two windings, designated a? and y, which are wound inductively, and, with the excepticn of the last B relay, six armatures, the first three and the last three of each relay being mechanically coupled by a similar bar of insulation. The last B relay has but five armatures, the first two and the last three being similarly coupled, respectively.

These relay trains are under the control of two main relays F and G which are operated by switches or keys L and M, respectively, and a trigger relay D which is operated by a switch or key U. A change in the totalatteniiation interposed by the attenuation pads may be accomplished by closing and opening either of the main relays F or G and by opening the trigger relay D, switch M being responsible for increasing the total effective attenuation, and switch L being responsible for decreasing the total effective attenuation.

The arrangement shown in the drawing represents the relay regulating circuit coinplete except for the apparatus required for the control mechanism actuating switches M, L and U. Alternating current is transmitted over the transmission circuit from the input side e to the output side j', and, while the input at e may vary within certain limits, it is desired to maintain the output at f automatically within much smaller limits, This is accomplished by cutting into or out of the transmission circuit one or more of the artificial line pads which are shown in units of 1, 2, 4r and 8 transmission units (TU) of attenuation, as has been stated hereinabove.

When the input at e varies to such an extent as to require adjustment ot the number subsequently closing and of pads in order to keep the output at f within the prescribed limits, the circuit is made automatically responsive to control mechanism which picks up through a high impedance transformer T a small portion of the output current. This control mechanism may be any one of a umher of suitable devices as, for example, the one known as the pilot indicator panel and Brown controller used in carrier telephone pilot channels, it being understood that other satisfactory de f'ices may equally well be employed herein. This control mechanism will interconnect the Vsecondary 'winding of transformer T with the switches L, M and U in any well-known manner, permitting switch U to be periodically closed and opened and either switch L or M to he kperiodically closed and opened as the output at f goes Vbeyond the predetermined lower or upper limit, respectively. rlhe closing and opening of switch U will be effectiveonly after either switch L or lll has been closed and opened. Changes in the attenuation will continue to take place the periodic closing and opening of either switch L or M and-of switch U, until, however, the output f has been brought within the prescribed limits by the interposition ofthe proper amount of attenuation in response to the actions of the relay regulating circuit.

The variations in alternating current flowing in 1Lhe transmission circuit may, of

' course, be due to any cause the effect of which it is desired to counteract, the mostA common cause arising from variations in weather conditions, Vas stated hereinabove. lt is to he noted that an alternating current of suitableVV frequency will ordinarily be transmitted over the transmission circuit for the purpose of actuating the control mechanism so that the control mechanism may'respond to changes in the magnitude of this current caused, forv example, hy the above-mentioned weather variations. Since, inthe case of a telephone circuit, there are also transmitted, at the same time other currents of widely dierentv and rapidly changing frequencies and magnitudes, it is then necessary for the control mechanism to be responsive only to the current of the frequency transmitted for regulating purposes. The proper sensitiveness and re-Y sponsiveness may be obtained by tuning the input circuit of he control mechanism, i. e., the circuit of the Vsecondary winding of transformer T, to Vthe regulating frequency )y means of a variable condenser, such as S, or the lilre. lf the variations in the alternating current used for regulating purposes which flows over the transmission circuit do not occur too rapidly to allow sufficient time for the control mechanism to function, the mechanism will keepV the output at f within or close to the prescribed limits. Y

Each attenuation pad is controlled by contacts l and 2 of the associated B relay, relays Bl, B2, B3 and B2 being each controlled by relays A1, A2, A3 and A2, respectively, and by the trigger relay D. When the output current at f departs beyond the pre- :scribedl limits, theY control mechanism` becomes responsive and the relay regulating circuit functions to operate or release certain of the relaysl A1, A2, A3 and A4, the particular operation of relays A1 and A2 being described hereinafter. As will be understood hereinafter, after a short interval of time, the operation of relays A1 andA2 is followed by the operation of the trigger relay D, causing the grounding of Contact l of relay l) and the oeation of the corresponding B relays, relays B1 and B2, particularly, through the contacts 3 of relays A1 and A2 ancL the windings designated 'y of relays Bl and B2. An instant later, contact 2 of relay D is opened, causing the release of any previously operated B relays, as, for example, relay B3 which may have been previously operated and locked through its Contact 5 and its m winding.

rlhe following table shows the values of attenuation obtainable -rom the four attenu ation pads having magnitudes of l, 2, A and 8 transmission units (TU) andthe conditionV of relays B1, B2, B3 and B4 which respectively control these pads and which must he operated toV obtain the proper magnitude of attenuation:

Itl should be noted that relay B2 is alternately operated and released for each successive valueof attenuation. lt shouldalso be Vnoted that relay B2 is alternately operated andreleased at each second value of attenuation. The same is true of relay B2, which is'k successively 'operated at every fourth value-of attenuation, and so on with other relaysv in the geometrical progression indicated. The relay regulating .circuit shown in Fig. 1 is arranged so that the required geometrical progression in the number of times the various relays operate and release is obtained. To show in greater detail how this takes place, it is necessary to trace this circuit in its operation through several typical steps.

The total attenuation may be stepped up by means of switch M which controls relay G, and this attenuation may be stepped down by means of swi cn L which controls relay F. Relay A1 is under the control of both relays F and G. When either relay F er operates, relay A1 operates, if released, or, if relay A1 has been previously operated, it releases, and this is always the case except at each end of the range of attenuation, as will be described hereinafter.

Vhen the rela' regulating circuit is in the condition shown in F ig. l, the total attenuation interposed in the transmission circuit is two transmission units. Suppose the input at e rises sufficiently to start the control mechanism in operation. In order to keep the output Vat f within narrow limits, the attenuation interposed in the transmission circuit must be increased.y The control mechanism closes switch M. It will be observed, upon an inspection of the above enumerated table, that a change in the attenuation from two to three transmission units requires the operation of relay Bl while relay B2 remains operated.

lVhen switch M closes, relay G operates, current flowing through the winding of relay G from battery C. A circuit is completed extending from ground through contact 2 of relay G, contact 9 of relay B1, contact 7 of relay Bl, the winding of relay A1, and resistance Rl to the ungrounded side of battery C. Accordingly, relay Al operates. Relay Al then becomes locked by the connection of one terminal of its winding to the grounded side of battery C through its contact 2. yThe closure of contact 1 of relay G accomplishes nothing at this time because, although contact 1 of relay A1 is closed for an instant before relay A1 operates, contact t of relay B1 and contact 1 of relay A2 are both open.

After a short interval, the control mechanism opens switch M, thereby releasing relay G. Shortly thereafter, the control mechanism closes switch U, causing the tripping relay D to operate by the flow of current through its winding from the battery C. The closure of contact 1 of relay D cempletes a circuit from ground through contact 3 of relay Al'and through winding y of relay B1y to the ungrounded side of bai;- tery C; Accordingly, relay B1 operates, and, upon closure of its contact 2 and upon opening of its contact l, adds the attenuation pad kof one transmission unit to the transmission circuit. Due to the make-before-break action of relay D, the opening of contact 2 of relay D an instant later does not release relay B2, because one terminal of winding y of relay B2 is connected to the grounded side of battery C through contact 3 of relay A2 and contact 1 of relay D, battery C supplying winding y of relay B2 with energizing current. This condition continues as long as relay D remains operated.

After a short interval of time, however, the control meclmnism opens relay U, thereby releasing relay D. Relays B1 and B2 become locked by the flow of current from battery C through their windings and their contacts 5, respectively, and also contact 2 of relay D which leads to the grounded side of battery C.

It will be apparent that the total attenuation interposed in the transmission circuit has been changed from two transmission units to three, and that this has been accomplished by successively closing and opening switch M followed successively by closing and opening switch U. The action of switch U is effective only after switch M has been operated and released.

If the output at is within the prescribed limits, the control mechanism vill cease to operate. If, however, the outputat f tends to go beyond the upper prescribed limit, the control mechanism will function to introduce additional attenuation. Switch M will again be closed. The table given hereinabove shows that change in the total attenuation from three transmission units to four requires the release of both relays B;L and B2 and the operation of relay' B3. Upon the closure of switch M, it will be apparent that relay G operates. Thus, the grounded side of battery C is connected through contact 2 of relay G, contact 9 of relays B3 and B4, which are in parallel relationship, and contact 6 of relay B1 to the junction of the winding of relay A1 and the resistance R1. Accordingly, the winding of relay A1 becomes short-circuited, causing its release. Resistance R1 prevents excessive current from flowing through the short-circuiting contacts.

Upon the release of relay A1, a circuit is established from the grounded side of battery C through contact l of relay G, contact 1 of relay A1, Contact l of relay B, and contact 6 of relay B2 to the junction of the winding of relay A2 and the resistance R2. Accordingly, the vinding of relay AL becomes short-circuited and this relay releases. Immediately upon the release of relay A2, a circuit is established from the grounded side of battery C through Contact 1 of relay G, contact 1 of relay A1, contact 1 of relay A2, cont-act a of relay B2, contact '7 of relay B3, the winding of relay A3, and the resistance R3 to the ungrounded side of battery C. Accordingly, relay A3 operates, and it becomes locked by virtue of the connection of one terminal of its winding to the grounded side of battery C through contact 2 of relay A3. Thus, relays A1 and A2 have been released and relay A3 has been operated` Subsequently, the control mechanism opens switch M, thereby releasing relay G. Shortly thereafter, switch U closes, operating relay D. Upon the closure of contact l of relay D, the grounded side of batteryV C becomes connected, through contact 3 of relay A3 and winding ,if orrelay B3, to the ungrounded side of battery C. Accordingly, relay B3 operates. Shortly thereafter, contact 2 of relay D is opened, causing the release of relays B1 and B2. Upon the opening of switch U and the release of relay D, relay B3 remains operated by virtue of the connection of the grounded side of battery C through Contact 2 of relay D,'contact 5 Y of relay B3 and winding a; of relay B3 to the ungrounded side of battery C.

Thus, a step has been completed for increasing the total attenuation interposed in a transmission circuit from a value corresponding to three transmission units to one corresponding to four transmission units.L

If it be assumed that this change in the total attenuation is sufficient to bring the output at f down within the prescribed limits, the control mechanism will cease to operate and switch M Vwill not be closed again. Y

Assuming the total attenuation to be at a value corresponding to four transmission units, and that the output at j decreasesv below the lower prescribed limit, it will then be necessary to .decrease the effective attenuation. A step downward may be taken by changing the attenuation from a value corresponding tov four transmission units to one corresponding to three units, this being accomplished by releasing the relays controlling the attenuation pad of fouriunits and operating the relays controlling the attenuation pads of one and two transmission units.

,Switch VL, when 'closed by the control mechanism, will cause relay F to operate, the-winding of relay Fbeing connected to battery G by means of switch L. A circuit will then be completed, extending from the grounded terminal of battery C through contact 2 of relay F, contact 8 of relay B3, contact 7 of relay B;L to winding of relay VA1 and the resistance R1 to the ungrounded terminal of battery C. Accordingly, relay A1 operates, and, upon closure of its contact 2, which is connected to the grounded terminal of battery C, becomes locked. Immediately upon the operation of relay A1, another circuit yis established from the grounded terminal of battery C through Vcontact 3 of relay B2 and Contact 6 of relay.

B3toy thejunction of the winding of relay A3 and the resistance YB3. Since both terminals of the winding of relay A3 are now connected to the grounded side of battery C, this winding is in effect short-circuited and its armatures become released. -Thus, relays A1 and A2 have been operated, and relay A3, released.

Subsequently, the control cuit is established from the grounded side of battery C through contactl of relay D, contact Blof relay A1, winding y of relay B1 to the ungrounded side of battery C. Accordingly, relay B1 operates. A circuit is also established from the grounded side of battery C through contact l of relay D, contact 3 of relay A2, winding jr/ of relay B2 to the ungrounded side of battery C. Therefore, relay B2 operates. Subsequently, upon the opening of contact 2 of relay D, contact 3 of relay A3 having previously been opened, relay B3 releases by virtue ofthe fact that neither of its windings is connected in series with the battery C.V

it is well to note that when the control mechanism opens switch U, a circuit is established from the grounded side of battery C lease relays A3 and B3 and to operate relays A'l and Bland relays A2 and B2, the latter pairs of relays controlling the attenuation pads corresponding to one and two transmission units, respectively. In kdecreasing the total effective attenuation, it was necessary to operate the control mechanism soV as to close and open switch L and to subsequently close and open switch U. .Further decreases in the total effective attenuation mechanism closes switch U, operating'relay D. A cir- `Y may be made in a similar manner, as required.

In general, then, it may be said that the circuit operates in such a manner while increasing the attenuation in successive steps corresponding to one transmission unit each, that any certain B relay, except relay B1, for instance, relay B3, becomes operated when a step is taken only after all the preceding B relays in ascending numerical order, in this case, relays Bl and B2, have been in the operated condition on the preceding step. And furthermore, the operation of any B relay, as the said B3, on the step in question, is accompanied by the release of all the preceding B relays, as the said Bl and B2. This will also be apparent upon inspection of the above table. Similarly, in decreasing the total attenuation in successive steps in magnitudes of one transmission unit each, any certain B relay, except relay B1, as, for example, relay B3, becomes released when a step is taken only when all of the preceding B relays in ascending numerical order, as, for example, relays Bl and B2, have been in the released condition on the preceding step. And furthermore, the release of any B relay, as the relay B2, on the step in question, is accompanied by the operation of all the preceding B relays, as, for example, relays Bl and B2. This condition will also be apparent upon further inspection of the above table. Relays A1 and B1, however, are both alternately operated and released foreach succesive step in attenuation, for it will be apparent from the table that an attenuation pad corresponding to one transmission unit must be alternately cut into and out of the circuit for each step, whether that step is taken upwardly or downwardly.

In stepping upwardly over the entire range of attenuation without interruption, or downwardly, it will be apparent that relay B1 is operated twice as often as relay B2, relay B2 twice as often as relay B3, and so on. The associated A relays-operate also with the same frequency. This geometric progression in relay operation represents one of the novel features of this invention and results in what seems to be a relay switching scheme having a minimum of relays for the switching operations.

An effective cut-0H of the relay circuit is provided at each end of the range of attenuation. If all of the attenuation pads-are interposed in the transmission circuit, and if the output at f goes above the upper prescribed limit, no further correction is possible. The control mechanism, however, continues to open and'close switch M in response to the abnormally high output. The next step after all of the attenuation pads have been switched into the transmission circuit would result in switching all of the pads out of the transmission circuit, if not prevented. Such an undesirable condition is indeed eliminated by making further stepping action, due to the movement of switch M and the action of the associated relay G, impossible when all of the B relays have been operated. It will be seen that contacts 9 of all of these B relays are connected in parallel between contact 2 of relay G and the winding of relay A1, and, since all of the contact-s 9 of these relays are opened, relay A1 will not operate, tepping action due to the movement of switch M cannot result as lon(r as this condition continues.

In a similar manner, contacts 8 of all of the B relays are connected in parallel between contact 2 of relay F and the winding of relay A1, and, since all of these contacts 8 are opened when all of the B relays are `eleased, any further stepping action due to the movement of switch L and the action of relay F will be prevented even though the output at is below the lower prescribed limit.

The relay circuit of this invention can be extended to cover any desired range of attenuation, no matter how large, by using the proper number of attenuation pads which are also of the proper size, under the condition, however, that each consecutive attenuation pad in the series is twice as large as the next smaller one. In the arrangements shown in the drawing, if it is desired to extend the range of the relay circuit by one step, an attenuation pad corresponding to sixteen transmission units and an associatedv pair of relays can be added at the upper limit, or, on the other hand, an attenuation pad corresponding to one-half of a transmission unit and the associated pair of relays can be added at the lower limit.

As suggested hereinabove, the relay arrangement of this invention is greatly advantageous over any other known relay arrangement because of the small number of relays required, and this is particularly so if the range of attenuation to be covered is large and the size of each step in that range is small. In applying the described relay arrangement to a transmission circuit requiring, for example, seven pads, only seventeen relays are required, seven pairs corresponding to the seven pads and three additional relays similar to relays F, G and D. In a particular arrangement of the prior art, it has been found necessary to employ approximately one hundred and forty relays to control the seven pads.

In the arrangement shown in Fig. l of the drawing, the regulating circuit is designed primarily for use with control mechanism which closes,y and opens either switch L or M and then closes and opens switch U, these switches being periodically closed and opened as long as the level of energy Howto the type or" control mechanism of the Y prior art, which merely closes andfopens switches L or lvl, as required, and is not equipped witha switch U. Fig. 2 shows the two relays F and Gr which are controlled bvswitches L and M, respectively, and a relay D without the corresponding switch U.` ln the arrangement of this gure, conl'acts l and 2 cie relay l, and contacts l and n of clays ll and G, perform their functions in exactly the same manner as do the corresponding elements in Fig. l, and it is therefore not deemed necessary to show the complete relay regulating circuit orp Fig. l.

Both relays F and G have a third contact, designated 3, thisr contact controlling tne action oi a train of slow-acting relays N1, N2, 'N3 N 1. rlhis train ot slow-acting relays controls the action of relay D. When either relay F or relay G is operated in the usual manner, contact 3 of the relay operatedY completes a circuit from ground through contact 3, the winding of relay N, to the ungrounded side orp battery C. Accordingly, relay N1 p1 tes, and yet, due to the slow-acting n t this relay, it requires a deiin lrval before contact l of this clay becomes closed. Upon the closure'otl contact l or" relay N1, a circuit is completed from ground through winding ot relay lll to the ungrounded site of battery C. Accordingly, relay N2 operates,rits contact Vbeing also closed after a definite time interval. Similarly, relays N3 and N4 are in turn operated, each requiring a turther time interval for the closure of their associated contacts. Vfhen relay G releases, relay N1 also releases. A circuit is now completed extending from ground through Contact 2 of relay N1, the contact of relay N4, the winding of relay D to the ungrounded side of battery C. lAccordingly,

relay D operates and accomplishes .the same purposes as are set 'forth in connection with the Yarrangeinents shown in Fig. l. After the release ot relay N1, however, relays N2, N3 and Nl become released inv succession. Finally, upon the opening of thecontact of relay N4 rela i Drreleases.

vt g 3 lt will be clearly understood, however,

Y that'while only four slow-acting relays have been shown herein for the purpose of illustration, any desired number of similar relays may be employed so that the associated relay l) may be operated and released within any desired space of time. Y

While thegeneral principles of lthis invention have been applied to certain particular'arrangements merely for the purpose of illustration, it will be Vunderstood that these principles may be embodied in other groups in a di'iixerent order to anclwiclely varied organizations Without departing from the spirit of the inventionand the scope of the appended claims.

Vhat is claimed is a I l. The combination of a plurality of elements of attenuation of magnitudes arranged ingeometric progression, a plurality of pairs ot relays, one pair of relays corresponding to each element oi' attenuation, means for operating one of the relays of cach pair before the other relay of that pair is operatea, and means Jfor operatingsaid pairs of relays in a predetermined order to change the attenuation by equal increments'.

2. rEhe combination of a plurality ofV elements of attenuation having magnitudes in geometric progression, a plurality of pairs of relays, one pair or said relays corresponding to and controlling each element of attenuation, meansy for operating one of the relays of each pair before the other relay et that pair is operated, means for operating said pairs of relays in a predetermined order to successively increase the attenuation in arithmetical progression, and means to operate said pairs of relays in the reverse order to successively decrease the attenuation in arithmetical progression. v

3. The combination of a plurality of attenuation pads having magnitudes which are successively in geometric progression, a plurality of pairs of relays, one pair oilV said relays corresponding to and controlling each attenuation pad, means for operating one of the relays ot each pair before the other relay ot' that pair is operated, means for successively operating said pairs of relays in groups in a predetermined order to increase the total attenuation of said pads in arithmetical progression, and mean for successively operating said pairs of relays in decrease the total attenuationiot said pads in arithmetical progression.

l. The combination ot' a transmission circuit in which signals may be transmitted, a plurality'oli4 attenuation elements which may be added to or subtracted from said transmission vcircuit to change its gain by any desired amount, a pair or" control relays, Vone control relay controlling the increasev in the number oi attenuation elements, the Vother control relay ,controlling the decrease in the attenuation elements, a master relayoperatively associated With both of said control relays, means to successively and alternately operate and release the iirst of said control relays and the master relay to increase the number Vof attenuation elements,and means to successively and alternately operate and release the second or'. the control relays and the master relayV as the number of attenuation elements is to be decreased. i

5. The combination-of a plurality of atllO lll

tenuation elements, a pair of control relays, a master relay operatively associated with both of said control relays, means to successively and alternately operate one of the control relays and the master relay as the attenuation of said elements is to increase, means to successively and alternately operate and control the other of the control relays and the master relay as the attenuation of said elements is to decrease, and means whereby said control relays and said master relay may effectively change the attenuation of said elements by any predetermined amount.

6. A regulating arrangement for a signal transmission circuit comprising a plurality of attenuation elements of magnitudes which are arranged in geometrical progression, a plurality of pairs of relays, one pair of relays corresponding to each attenuation element and controlling its connection to the transmission circuit, means to operate one of the relays of each pair before the other relay of that pair has been operated, means to operate said pairs of relays in selected groups so as to consecutively change the total attenuation of said elements in arithmetical progression, means to prevent the simultaneous release of all of said pairs of relays after all have become operated, and means to prevent the simultaneous operation of all of the pairs of relays after all have become released.

7. The combination of a transmission circuit transmitting signals, a plurality of attenuation elements Which may be added to or taken from the transmission circuit to change the total attenuation of the transmission circuit by any desired amount, a pair of control relays, a third relay operatively associated With said control relay, one of said control relays and said third relay being successively and alternately operated and released to increase the total attenuation, the other of said control relays and said third relay being successively and alternately operated and released to decrease the total attenuation, and means whereby said pair of control relays and said third relay may effectively change the total attenuation of said elements by any desired amount.

In testimony whereof, I have signed my name to this specification this 31st day of October, 1928.

RUSSELL H. LINDSAY. 

